@makzan Sorry, there's a 45 MB limit for the uploads. It's a little clunky but it is possible to unzip the Tumblr export and essentially split the images (which take up the most room) into smaller .zip files that can be imported. Email help and I can provide some more detailed instructions if you want to try that!
@makzan It shouldn't create duplicates... The import is designed so that it can be run multiple times and will just update existing posts. Can you check this logs page and see if there's any mention of running the import? If not, email help... I may need to look at the ZIP file and see what's going wrong.